007759   Gupta V;Singh Y P;Badruddin (Physics Dep, Aligarh Muslim Univ, Aligarh-202 002, Email: badr_phys@yahoo.co.in) : Characteristic features of ICMEs associated with big storms in geomagnetic activity and large forbush decreases in cosmic ray intensity. Indian J Radio Space Phys 2010, 39(5), 265-9.

The solar sources and features of interplanetary structures associated with big geomagnetic storm (GS) and/or large Forbush decrease (FD) events have been investigated. The hourly data of geomagnetic activity, cosmic ray (CR) intensity, and solar wind plasma/field has been utilized during the passage of ICME_s and associated structures (e.g. shock/seam, interaction region/high speed stream). The geo-effectiveness and CR-effectiveness of ICME_s, similarities and distinctions between them together with variations/fluctuations in interplanetary plasma/field parameters is utilized in order to identify distinct feature(s) of ICMEs and physical mechanism(s) playing important role in the development of GS and FD.

4 illus, 15 ref

007758   Gosain S;Venkatakrishnan P (Udaipur Solar Observatroy, Physical Research Laboratory, Udaipur-313 001, Email: sgosain@prl.res.in) : Solar Vector magnetograph: instrument status and vector field measurements of non-flaring solar active regions. Indian J Radio Space Phys 2010, 39(5), 319-24.

The Solar Vector Magnetograph (SVM) of Udaipur Solar Observatory (USO) is an imaging polarimeter based on a aunable Fabry-Perot filter. In the present paper, the development efforts during phase-II of this instrument have been presented. These include: (i) installation of the instrument on a new robotic mount at the island site of USO; (ii) polarimetric calibrations of the instrument; and (iii) development of tools for performing data reduction and Stokes inversion. In particular, the Milne-Eddington inversion of polarized line profiles of the entire active region using parallel computing concept is described. Finally, few preliminary results regarding the vector magnetic field and other activity parameters of sunspots in non-flaring solar active regions are discussed. Such observations serve as a reference for comparison with flaring active regions.

4 illus, 13 ref

007757   Gopalswamy N;Xie H;Yashiro S;Usoskin I (NO, NASA Goddard Space Flight Center, Gode 695 Greenbelt, MD 20771, USA) : Ground level enhancement events of solar cycle 23. Indian J Radio Space Phys 2010, 39(5), 240-8.

Ground level enhancement (GLE) events, typically in the GeV energy range, are the most energetic of solar energetic particle (SEP) events with the protons penetrating Earth's neutral atmosphere. During solar cycle 23, sixteen GLE events were observed with excellent data coverage of associated solar eruptions. The source of these GLE particles has been examined in this paper using white light observations of coronal mass ejections, type II radio bursts, and soft X-ray flares. It has been shown that the GLE events are consistent with shock acceleration in every single case. While the possibility of the presence of a flare component during GLE events cannot be ruled out, it can be definitely said that a shock component is present in all the GLE events. During 18 April 2001 GLE event, the source was located <126>30 degrees behind the west limb, which is too far away from the magnetic field lines connecting Earth and hence the flare component can be ruled out. Also the presence of interplanetary shocks associated with the GLEs is shown using radio and in-situ observations.

6 illus, 2 tables, 18 ref

007756   Gayathri R;Samuel Selvaraj R (NO, Dhanalakshmi Srinivasan College of Engg. & Tech., Poonjeri, Mamallapuram, Chennai-603 104, Email: r.gayathri77@rediffmail.com) : Predictability of solar activity using fractal analysis. J Indian Geophys Union 2010, 14(2), 89-92.

Various new techniques like neural networks, learning nonlinear dynamics and others are used by researchers to predict solar activity. But we are yet to obtain reasonably good results. This is mainly because the reason of the variation of solar activity is still unknown. Hence it is important to analyze the characteristics of the data. This paper considers sunspot numbers as an index of solar activity. The daily sun spot number data is analyzed using fractal technique and examined to determine the predictability of solar activity. For the period 1990 to 2004, the average fractal dimension for periods of 10 days or less was about 1.43. But during the same period, the average fractal dimension was 1.72 for periods longer than 10 days. Hence the result is encouraging for short-term prediction (i.e.) within about 10 days, but discouraging for medium-term prediction (longer than 10 days).

2 illus, 1 table, 3 ref

007755   Dwivedi V C;Pandey V S;Tiwari D P;Agrawal S P (Physics Dep, A P S Univ, Rewa, Madhya Pradesh-486 003, Email: vidya_charan2000@yahoo.com) : Effect of solar wind speed variations on other interplanetary parameters. Indian J Radio Space Phys 2010, 39(5), 252-6.

The daily values of interplanetary solar wind parameters as well as that of the geomagnetic disturbance index (Ap) have been used for the years 1965-2006. Long-term averages have been calculated for all those days when simultaneous data is available for all these parameters (V, B, Bz and Ap). Earlier reports have usually underlined the importance of V in producing terrestrial effects. As such, individual days have been grouped, in accordance with the limited range of V, in seven groups by the method of iteration using K-mean clustering (data mining) technique. Having selected days in each of the seven groups (ranges), the group averages, have been calculated for the entire period for V, B, VB and Ap along with their standard errors. The method has been further repeated for the individual solar cycles. These group averages have been used to investigate the statistical relationships between V, B, VB and Ap in different combinations. The results so obtained can be summarized as: (i) the monotonic increase of group average V is almost similar to that of increasing average values of Ap, and VB from groups 1 to 7; (ii) For each of the seven groups, VB vs Ap and B vs Ap have been always found to be better correlated ('r' larger) on a day-to-day basis, whereas V vs Ap has low values of V; (iii) the direction of Bz when negative is very much effective in producing larger Ap as compared to days when Bz is positive, in all the seven groups (more prominently in the last four groups of larger V). The statistical results obtained signify that the product VB is very effective in producing large scale geomagnetic disturbances.

2 illus, 27 ref

007754   Dickson Benjamin A;Prabhakaran Nayar S R (Physics Dep, N M Christian College, Marthandem-629 165) : Characteristics of interplanetary CMEs observed by ulysses. Indian J Radio Space Phys 2010, 39(5), 270-5.

The characteristics of discontinuities associated with interplanetary coronal mass ejections and their distribution in the heliosphere have been studied in detail. For this, jumps in solar wind plasma parameters like wind velocity, IMF and proton density across the shocks and discontinuities have been evaluated and used to characterize them. The distribution of the plasma parameters across the discontinuities with respect to heliolatitude and with radial distance from the Sun have been analyzed using the Ulysses data taken during its three orbits around the Sun.

3 illus, 11 ref

007753   Das M K;Narang P;Yuasa M;Saha L M (Institute of Informatics and Communication, Delhi South Campus Univ, New Delhi-110 021) : Simulation and characterization of trajectories in sun-jupiter-comet system. Indian J Radio Space Phys 2010, 39(5), 137-9.

The trajectories of a comet in the Sun-Jupiter system have been simulated within framework of restricted three body problem. Specific case of the comet Oterma/cometary dust have been considered. In this investigation, effect of radiation from the Sun has been incorporated parametrically in terms of (β, ratio of the force due to radiation pressure and force of gravitational attraction from Sun. Phase space of the motion of comet/cometary dust has been analysed for regular and chaotic motion using Poincare surface of section method (SOS) and also the spatio-temporal pattern analysis.

4 illus, 13 ref

007752   Chandra H;Sharma S;Aung S W (NO, Physical Research Laboratory, Ahmedabad-380 009, Email: hchandra@prl.res.in) : F-region variability over the anomaly crest region. Indian J Radio Space Phys 2010, 39(5), 302-7.

Day-to-day variability in the critical frequency of F-layer (f₀F₂) over Ahmedabad has been examined. The hourly data for the months of January, March and July for the high sunspot year 1969 and low sunspot year 1996 have been analysed to study the variability. Daily variations on different days of the month, standard deviations and the normalized deviations at each hour have been studied. The normalized standard deviations are up to ±30% during night hours and up to ñ15% during day hours. While the variability during day hours is mainly because of the variability in the electric field (electrojet strength) that gives rise to vertical drift and subsequent ionization anomaly, the variability during night hours is also contributed by the variability in thermospheric neutral winds and temperature.

3 illus, 27 ref

007751   Bangia T;Bhattacharjee S;Guharay A;Taori A (NO, Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital-263 129) : Upper atmospheric emissions using mesosphere lower thermosphere photometer (MLTP) designed at ARIES. Indian J Radio Space Phys 2010, 39(5), 325-9.

Mesosphere Lower Thermosphere Photometer (MLTP) has been designed at ARIES for studying mesosphere lower thermosphere coupling processes. MLTP utilizes f/2 optics with 4° circular field of view. It has seven narrow bandwidth (FWHM <126> 4 Å) interference filters mounted on a geared filter plate housed in filter chamber under precise temperature controlled conditions. Out of these seven filters, filter at 630 nm is meant to monitor ionospheric F- region airglow emission due to atomic oxygen. MLTP has been successfully installed and made operational at Space Weather Laboratory of ARIES.

5 illus, 8 ref

022317   Nath B (NO, Raman Research Institute, Bangalore-560 080, Email: biman@rri.res.in) : Enigma of cosmic rays-1. Resonance 2007, 12(10), 6-17.

Cosmic rays are energetic particles that zoom through space and occasionally enter our atmosphere. They are believed to be produced by violent astronomical events in and outside our Galaxy. Study of these particles provides a glimpse into the fascinating world of high energy physics.

5 illus, 2 ref

021225   Sharma D K;Sharma P K;Rai J;Garg S C (Applied Sciences, Manav Rachna College of Engineering, Faridabad-121 001, Email: dksphdes@rediffmail.com) : Effect of solar activity on ionospheric temperatures in F2 region. Indian J Radio Space Phys 2008, 37(5), 319-25.

Ionospheric F-region is very dynamic and highly depends on the solar cycle. In the present study almost half of the solar cycle from January 1995 to December 2000 (from solar minimum to solar maximum) satellite data were used. The data were recorded with the help of Retarding Potential Analyzer (RPA) payload aboard Indian SROSS-C2 satellite at an average altitude of 500 km over the Indian region. The data analysis shows that the nighttime average ionospheric electron and ion temperatures show a positive correlation with solar activity. However, the sunrise peak values show anti-correlation with solar activity. Further the ratio of sunrise average peak value and nighttime average show a negative correlation with the solar activity, both for electron and ion temperatures. A sudden enhancement at sunrise has been observed during all seasons, in both electron and ion temperatures. Comparison of the measured ionospheric electron and ion temperatures with the predicted values from the international reference ionosphere (IRI) reveals that the peak during sunrise hours is slightly underestimated by the IRI model.

021224   Radhakrishnan S R;Satyanarayana M;Mahadevan Pillai V P;Presennakumar B;Ramakrishna Rao D;Murthy V S (Optoelectronics Dep, University of Kerala, Trivandrum-695 581, Email: drsatyanarayana.malladi@gmail.com) : Lower atmospheric water vapour measurement at coastal Trivandrum (8.33°N, 77°E) using a high resolution Raman lidar. Indian J Radio Space Phys 2008, 37(5), 353-9.

Near simultaneous measurement of atmospheric aerosol and water vapour is described, making use of the Nd: YAG laser based multiwavelength lidar system, designed and developed in-house at Space Physics Laboratory, Vikram Sarabhai Space Centre, Trivandrum, India. In the present study, the vibrational Raman scattered signals of N₂ and H₂O were used for the measurement of atmospheric water vapour and aerosol extinction. Nighttime water vapour profiles are obtained in the 1-6 km altitude regions in the lower troposphere. Necessary aerosol corrections to water vapour profiles are also done. Lidar derived water vapour profiles are compared with the profiles calculated from High resolution Regional Weather Model (HRM) available during the same period.

021223   Mishra R K;Mishra R A (Computer and IT Section, Tropical Forest Research Institute, P.O. RFRC, Mandla Road, Jabalpur-482 021, Email: rkm_30@yahoo.com) : Solar cycle dependence of low amplitude anisotropic wave train events. Indian J Radio Space Phys 2008, 37(5), 312-8.

A large number of low amplitude anisotropic wave train events (LAEs) of cosmic ray diurnal anisotropy have been studied during 1980-1994 as a function of solar activity represented by sunspot numbers using the hourly neutron monitor data of Deep River station. The amplitude as well as direction of the diurnal anisotropy is well correlated with solar cycle during low amplitude days. The time of maximum for all days lies along 1650 hrs LT direction and is mostly caused by depression of cosmic ray intensity along garden hose direction or the increase of the intensity along anti-garden hose direction similar to that of high amplitude events. However, the direction of anisotropy for LAEs shows a preferential direction along <126>1250 hrs LT direction and this may be attributed to the increase in diffusion of particles perpendicular to interplanetary magnetic field lines. The shift of time of maximum along <126>1250 hrs LT direction for LAEs may be attributed to the increase in diffusion of particles perpendicular to interplanetary field lines. However, the shift of time of maximum for LAEs along 1550 hrs LT direction is mainly caused by corotation of cosmic ray particles along with solar system magnetic fields similar to that of normal diurnal variation. The occurrence of LAEs is solar activity dependent. It may be concluded that interplanetary turbulences responsible for cosmic ray modulation effects do not reach the Earth during solar minimum and maximum, which results in the dominance of LAEs during these periods. The increase in diurnal amplitude of LAEs during solar minimum and maximum is contributed by the additional flow of cosmic ray particles due to corotating streams.

021222   Jana P K;Sarkar D;Das P (Chemistry Dep, Government College of Education, Banipur, North 24-Parganas-743 233) : Effect of long-term ozone trend on night airglow intensity of Li 6708 Å at Dumdum (22.5°N, 88.5°E) and Halley Bay (76°S, 27°W). Indian J Radio Space Phys 2008, 37(5), 326-32.

The effect of O₃ depletion on night airglow emission of Li 6708 Å line at Dumdum (22.5°N, 88.5°E), India and Halley Bay (76°S, 27°W), a British Antarctic Service Station. Calculations based on chemical kinetics show that the airglow intensity of Li 6708 Å line will also be affected due to the depletion of O₃ concentration. The nature of yearly variation and seasonal variation of intensity of Li 6708 Å line for the above two stations are shown and compared. It is shown that the rate of decrease of intensity of Li 6708 Å line is comparatively more at Halley Bay due to dramatic decrease of Antarctic O₃ concentration.

021221   Devi M;Barbara A K;Saikia M;Chen W (Physics Dep, Gauhati University, Guwahati-781014, Email: md555@sify.com) : Vertical distribution of optical parameters of aerosols using Portable Automatic Lidar system of Gauhati University. Indian J Radio Space Phys 2008, 37(5), 333-40.

The features of a Portable Automated Lidar (PAL), operated at Guwahati (26°N and 92°E) are presented in this paper. The system has been used to determine vertical distribution of optical parameters of aerosols. The paper also describes a method adopted for profiling of aerosol extinction coefficient along with calibration of the lidar system. The extinction coefficient values of aerosols for dust-free and dusty situations are also presented.

020196   Vijayakrishnan M V;Sreehari C V;Mathew T J; Prabhakaran Nayar S R (Physics Dep, University of Kerala, Kariavattom, Thiruvananthapuram-695 581, Email: srp@md2.vsnl.net.in) : Influence of IMF Bz on the variability of the minimum value of f_°-F2. Indian J Radio Space Phys 2008, 37(1), 46-50.

The critical frequency of the ionosphere, apart from the diurnal and annual variations exhibit day-to-day variations. The minimum value of f_°-F2 around the pre-sunrise period also has a day-to-day change. In this work, the relation between the magnitude of fo-F2 minimum and h'F2 values around the pre-sunrise period and their relation with the sign of the north-south component of the interplanetary magnetic field (IMF) is investigated. The minimum value of f_°-F2 for each day is found to be related to the IMF north-south component, with the f_°-F2 value tending to be larger when the IMF is northward and smaller when the IMF is southward. The northward IMF B_z is seen to produce an eastward electric field at the ionosphere and move the ionospheric plasma to higher altitudes resulting in higher critical frequencies. Whereas a southward IMF B_z produce a westward electric field and move the ionospheric plasma to lower altitudes resulting in lower critical frequencies.

020195   Sengwa R J;Soni A (Dielectric Research Lab, Department of Physics, J N V University, Jodhpur-342 005, Email: rjsengwa@rediffmail.com) : Dielectric properties of some minerals of western Rajasthan. Indian J Radio Space Phys 2008, 37(1), 57-63.

Dielectric constant ε' and loss ε" of dry samples of clay, siliceous earth, fuller's earth, gypsum, lignite, calcite, tourmaline and magnesium rock of opencast mines of western Rajasthan, India, were studied in the frequency range 100 Hz - 100 kHz and also at X-band microwave frequencies. It is observed that the values of ε' decreases with increase in frequency in low frequency region. Exceedingly high ε' values were found for clay, siliceous earth and, fuller's earth at lower frequencies in the 100 Hz to 100 kHz frequency range. The complex plane plots (ε" versus ε') of these minerals are the Cole-Cole arcs. The low frequency limiting dielectric constant ε_o, high frequency limiting dielectric constant ε_∞, relaxation time of dipole rotation τ and, distribution parameter a of these materials were determined using the Cole-Cole plots. All these minerals have large value of α, and their τ values varies in the range from ≈ 0.1 to 11 ms. Frequency dependent ac conductivity of these minerals has been determined and discussed and, the contribution of sample bulk density and percent weight of the constituents of their chemical composition on the microwave values of ε' and ε" has been explored for the studied samples.

020194   Sekar R;Chakrabarty D (Physical Research Lab, Navrangpura, Ahmedabad-380 009) : Equatorial spread-F research in India: a brief review. Indian J Radio Space Phys 2008, 37(1), 7-27.

The Equatorial Spread-F (ESF) is a complex phenomenon encompassing a wide range of scale sizes (covering more than six orders of magnitude) of irregularities in electron and ion densities as well as in electric fields. The generation mechanisms involve not only the plasma processes but also neutral processes. Thus, to understand the different facets of ESF manifestations, investigations have been carried out using multiple techniques. The research in this topic has practical implications as these irregularities affect the propagation of radio wave even in Ultra High Frequency band. Considerable amount of works have been done in India to understand this phenomenon. Some of the important results in the last three decades, as perceived by the authors, are reviewed in this paper. This involves results obtained from ground-based, rocket and satellite borne experiments conducted from India along with theoretical and laboratory simulations.

020193   Mishra A P;Mishra B N;Gupta M;Mishra V K (Physics Dep, A P S University, Rewa-486 003, Email: apm_apsu@yahoo.co.in ) : Heliographic distribution of bright solar flares and association of Forbush-decreases with flares and coronal mass ejections. Indian J Radio Space Phys 2008, 37(4), 237-43.

Major solar flare events have been selected to study the heliographic distribution of solar flares during solar cycle 23. The occurrence of Forbush decreases (FDs), bright solar flares; solar flare index, coronal mass ejections (CMEs), average solar magnetic field and solar wind velocity have been studied for the period 1996-2006. It is found that the solar flare index in northern and southern hemisphere represents the cumulative activity of solar flare in both hemispheres. Though, the bright solar flares are equally distributed in the entire solar region, majority of the bright solar flares responsible for FDs (≥ 4 magnitude) are located in the north-east region of the solar disk. Out of 41 FDs, 88% are found to be associated with halo (central position angle ≈ 360°) and partial halo (central position angles ≥ 120°) CMEs (coronal mass ejections) and 55% with bright solar flares of importance ≥ 1B. The abrupt increase in average solar magnetic field and solar wind velocity has also been found to be a necessary condition for producing FDs. The occurrence of non-recurrent type FDs are more frequent than recurrent type FDs. In latitudinal distribution, northern hemisphere is more dominant than the southern hemisphere in producing FDs. It is also found that eastern hemisphere is more effective as compared to western hemisphere to produce FDs in longitudinal distribution during the aforesaid period.

020192   Kulkarni V H;Muralikrishna P (NO, , 10 Archen Co-Op Housing Society, Sector-4, Vashi, New-Bombay-400 703) : Effect of dust particles on two-stream instability: a possible explanation for the persistence of ionization trails of Leonid meteor showers. Indian J Radio Space Phys 2008, 37(1), 34-8.

Assuming a collisional plasma having dust particles and only electrons are magnetized, the two-stream instability is studied for the excitation of low frequency waves. The production and losses of both ions and electrons are included. In the absence of production, it is shown that losses by attachments of both ions and electrons on dust particles, two-stream instability require the drift velocity greater than ion acoustic velocity. The growth rate is reduced and the wave amplitude at saturation is reduced. Therefore the generation and magnitudes of ionization density irregularities is reduced. It is expected that the cross-field diffusion of ionization due to wave turbulence is affected. It is known that during meteor shower periods the E-region of the ionosphere has a significant number of dust particles. Therefore density irregularities in the ionosphere are modified. Also amplitude dependent diffusion rate is reduced. It is suggested that the presence of dust particles may be a reason for persistence of ionization trails seen for longer periods during Leonid meteor showers.

020191   Kane R P (NO, Instituto Nacional de Pesquisas Espaciais - INPE, C. P. 515, 12245-970 - Sao Jose dos Campos, SP, Brasil, Email: kane@dge.inpe.br) : Cosmic ray anisotropies during the Oct. 28-31, 2003 Halloween event. Indian J Radio Space Phys 2008, 37(1), 28-33.

Using data from the Nagoya muon directional telescopes during the storm of 29 Oct. 2003, the anisotropies were traced at successive UT times. Some features were very prominent, positive in some directions, negative in others. In each, different directional telescopes indicated different magnitudes, implying large directional anisotropies. By tracing the anisotropies in space, one could conclude that the Earth was engulfed by the interplanetary blob and passed slightly in its northern part (same as North of Sun). These results are approximate, as the simple analysis was carried out assuming straight line paths for cosmic rays, while some bending in magnetic fields and some scattering may be involved. Nevertheless, useful information can be obtained even from one muon set up as shown here. Using more copious data from other sources would, of course, give more detailed information.

020190   De S S;Paul S N;De M;De B K;Bandyopadhyay B (Centre of Advanced Study in Radio Physics and Electronics, University of Calcutta, Kolkata 700 009) : Field solution within the ionospheric anisotropic plasma in presence of thunderstorm and lightning. Indian J Radio Space Phys 2008, 37(1), 51-6.

In the presence of thunderstorm and lightning, Maxwell's equations for the ionospheric anisotropic plasma have been solved, considering the influence of geomagnetic field and time-varying random irregularities developing an ac magnetic field. This analysis has been used to study the electrodynamics of middle atmosphere during thunderstorm and lightening. The variations of thundercloud and lightning induced electric field have been numerically estimated for some specific ionospheric height range. The fluctuation of electron number density within the medium is also studied.

020189   De M;De S;Bhattacharya A B (University Science Instrumentation Centre, University of Kalyani, Kalyani-741 235) : Parallel architecture and algorithms for space weather prediction - a review. Indian J Radio Space Phys 2008, 37(3), 157-73.

Critical review is presented in this paper on parallel computing, including parallel algorithms and parallel architectures. Emphasis is laid on different interconnection networks, including recent efficient multi-mesh network. The role of parallel computing for design and analysis of adaptive sampling are pointed out. Different parallel computing platforms and their basic characteristics, along with some computing paradigms that are used in conjunction with adaptive designs are discussed. Some fundamental physical and numerical issues related to constructing modern numerical MHD codes for space weather prediction are outlined. Efficient execution of scientific simulations on high-performance parallel computers is focused. Scope for future development is also suggested.

020188   Calla O P N;Parihar V;Joshi N D;Chakravorty G;Rathore U (NO, International Center for Radio Science (ICRS), "OM NIWAS" A-23 Shastri Nagar, Jodhpur-342 003) : Method for calibration of space borne passive microwave sensors using a desert area. Indian J Radio Space Phys 2008, 37(4), 285-90.

New method is suggested for on-flight calibration of passive sensors, using a desert area, from satellite data obtained over a uniform terrain. The satellite data of OCEANSAT I MSMR payload operating at 6.6 GHz in both horizontal and vertical polarization and having look angle of 49.7° have been used for the study.

020187   Bose S K;Sarkar S;Bhattacharyya A B (Physics Dep, University of Kalyani, Kalyani-741 235) : Jovian decametric radio emission: an overview of the planetary radio astronomical observations. Indian J Radio Space Phys 2008, 37(2), 77-108.

Presents an overview of the Jovian decametric (DAM) radio emission up to the recent years. Evidences for periodic modulation of Jupiter's DAM radio emission are considered first. Information of Io (Jupiter's Galilean satellite) and non-Io related source location and their characteristic features of emission, e.g., polarization, shape of the beam, L-bursts, S-bursts, N-bursts, modulation lane etc. are discussed. Broadband electrostatic noise and field aligned current sources at Earth and Jupiter have been taken into account. The scope and direction for further investigations is also pointed out.

020186   Anil Kumar C P;Panneerselvam C;Nair K U;Jeeva K;Selvaraj C;Gurubaran S;Rajaram R (Equatorial Geophysical Research Lab, Indian Institute of Geomagnetism, Krishnapuram, Tirunelveli, Tamilnadu-627 011, Email: cpanil@iigs.iigm.res.in) : Influence of coronal mass ejections on global electric circuit. Indian J Radio Space Phys 2008, 37(1), 39-45.

Deals with the elucidation of flow of particles and field from the sun into the terrestrial system and their subsequent role in Global Electric Circuit (GEC). Many flare associated Coronal Mass Ejections (CMEs) have been studied from ACE satellite data during the last phase of the 23rd solar cycle. Such solar ejections consist of hot electrons, protons and helium ions embedded in magnetic fields of various intensities and which travel with velocities greater than supersonic speed towards the earth and breach terrestrial magnetic fields (under favourable conditions) and cause geomagnetic storms. Contemporary data of geoelectrical measurements made at the high latitude Indian Antarctic Research Station, Maitri (70.45°S, 11.44°E) have also been used to investigate the electrical processes during, before and after the above events. The study leads to the conclusion that CMEs enhance the population of the multi-ion plasma species, which paves the way for an increase in the overhead ionospheric electric potential during the onset or even up to the main phase of the magnetic disturbance. The near earth electrical environment is besieged with magnetic disturbance at the high latitude.

019286   Karmakar S;Mukherjee S;Sharma R;Maharaj S D (Physics Dep, North Bengal Univ, Darjeeling-734 430, Email: karma@iucaa.ernet.in) : Role of pressure anisotropy on the maximum mass of cold compact stars. Pramana J Phys 2007, 68(6), 881-9.

Studies the physical features of a class of exact solutions for cold compact anisotropic stars. The effect of pressure anisotropy on the maximum mass and surface red-shift is analysed in the Vaidya-Tikekar model. It is shown that maximum compactness, red-shift and mass increase in the presence of anisotropic pressures; numerical values are generated which are in agreement with observation.

4 illus, 2 tables, 29 ref

017060   Sharma R;Maharaj S D (NO, , ) : On surface tension for compact stars. J Astrophys Astr 2007, 28(2-3), 133-8.

In an earlier analysis it was demonstrated that general relativity give s higher values of surface tension in strange stars with quark matter than neutron stars. Generates the modified Tolman-OppenheimerªVolk off equation to incorp ate anisotropic matter and use this to show that pressure anisotropy provides for a wide range of behaviour in the surface tension than is the case with isotropic pressures. In particular, it is possible that anisotropy drastically decreases the value of the surface tension.

1 illus, 1 table, 30 ref

017059   Prasad J (Harish Chandra Res Inst, , Allahabad-211 019, Email: jayanti@mri.ernet.in) : Effects of the size of cosmological N-body simulations on physical quantities- II: halo formation and destruction rate. J Astrophys Astr 2007, 28(2-3), 117-31.

Shows how errors due to finite box size affect formation and the destruction rate for haloes in cosmological N-body simulations. In an earlier study author gave an analytic prescription of finding the corrections in the mass function. Following the same approach, analytical expressions were given for corrections in the formation rate, destruction rate and the rate of change in comoving number density, and compute their expected values for the power law (n = -2) and LCDM models.

6 illus, 43 ref

017058   Pant T K;Vineeth C;Sridharan R (Space Physics Lab, Vikram Sarabhai Space Center, Trivandrum 695 022, Email: tarun_kumar@vssc.gov.in) : Daytime optical investigation of the equatorial mesopause energetics in the context of equatorial MLTI coupling: Recent results. Indian J Radio Space Phys 2007, 36(6), 514-25.

First experimental evidences for the mesopause energetic changes in context of (a) counter electrojet (CEJ); (b) solar flare; and (c) solar eclipse in the equatorial mesopause region using a daytime optical photometer are presented. The photometer has been operated in a scanning mode to probe the thermosphere and mesopause regions simultaneously in north-south direction over Trivandrum (8.5°N; 77°E; dip lat. 0.5°N). The striking features observed are (i) enhancement in the wave activity as seen in the mesopause temperature, during the eclipse, (ii) cooling of the mesopause during the equatorial electrojet (EEJ) reversal and (iii) decrease in mesopause temperature during a flare. These observations are discussed to highlight the vertical coupling of the mesopause with thermosphere-ionosphere region, mainly through neutral dynamics.

017057   Narlikar J V (Mathematics Dep, Autonomous Univ of Zacatecas, Zacatecas, ZAC C.P. 98060, Mexico, Email: jvn@iucaa.ernet.in) : Cosmology and cosmogony in a cyclic universe. J Astrophys Astr 2007, 28(2-3), (NULL).

Discusses the properties of the quasi-steady state cosmological model (QSSC) developed in 1993 in its role as a cyclic model of the universe driven by a negative energy scalar field. Discusses the origin of such a scalar field in the primary creation process first described by F. Hoyle & J. V. Narlikar forty years ago. It is shown that the creation processes which take place in the nuclei of galaxies are closely linked to the high energy and explosive phenomena, which are commonly observed in galaxies at all redshifts. The cyclic nature of the universe provides a natural link between the places of origin of the microwave background radiation (arising in hydrogen burning in stars), and the origin of the lightest nuclei (H, D, He³ and He⁴). It also allows us to relate the large scale cyclic properties of the universe to events taking place in the nuclei of galaxies. Observational evidence shows that ejection of matter and energy from these centers in the form of compact objects, gas and relativistic particles is responsible for the population of quasi-stellar objects (QSOs) and gamma-ray burst sources in the universe. Discusses the major unsolved problems of this integrated cosmological and cosmogonical scheme - the understanding of the origin of the intrinsic redshifts, and the periodicities in the redshift distribution of the QSOs.

1 illus, 80 ref

017056   Lopez Corredoira M (Instituto de Astrofisica de Canarias, , C/.Via Lactea, s/n, E-38200 La Laguna (S/C de Tenerife), Spain, Email: martinlc@iac.es) : Some doubts on the validity of the foreground galactic contribution subtraction from microwave anisotropies. J Astrophys Astr 2007, 28(2-3), 101-16.

The Galactic foreground contamination in CMBR anisotropies, especially from the dust component, is not easily separable from the cosªmological or extragalactic component. In this paper, some doubts will be raised concerning the validity of the methods used until now to remove Galactic dust emission and will show that none of them achieves its goal. Reviews the recent bibliography on the topic and discusses critically the metho s of foreground subtraction: the cross-correlation with templates, analysis assuming the spectral shape of the Galactic compoªnents, the "maximum entropy method", "internal linear combination", and "wavelet-based high resolution fitting of internal templates". Second, I analyse the Galactic latitude dependence from WMAP data. The frequency dependence is discussed with data in the available literature. The result is that all methods of subtracting the Galactic contamination are inaccurate. The Galactic latitude dependence analysis or the frequency dependence of the anisotropies in the range 50-250 GHz put a constraint on the maximum Galactic contribution in the power spectrum to be less than ~ 10% (68% L.) for an ~ 1 degree scale, and possibly higher for larger scales. The origin of most of the signals in the CMBR anisotropies is not Galactic. In any case, the subtraction of the galaxy is not accurate enough to allow a "precision Cosmology"; other sources of contamination (extragalactic, solar system) are also present.

1 illus, 85 ref

017055   Li K J;Li Q X;Gao P X;Mu J;Chen H D;Su T W (National Astronomical Observatories/Yunnan Observatory, , CAS, Kunming-650 011, Email: lkj@ynao.ac.cn) : Activity cycle of solar filaments. J Astrophys Astr 2007, 28(2-3), 147-56.

Long-term variation in the distribution of the solar filaments observed at the Observatorie de Paris, Section de Meudon from March 1919 to December 1989 is presented to compare with sunspot cycle and to study the periodicity in the filament activity, namely the periods of the coronal activity with the Morlet wavelet used. It is inferred that the activity cycle of solar filaments should have the same cycle length as sunspot cycle, but the cycle behavior of solar filaments is globally similar in profile with, but different in detail from, that of sunspot cycles. The amplitude of solar magnetic activity should not keep in phase with the complexity of solar magnetic activity. The possible periods in the filament activity are about 10.44 and 19.20 years. The wavelet local power spectrum of the period 10.44 years is statistically significant during the whole consideration time. The wavelet local power spectrum of the period 19.20 years is under the 95% confidence spectrum during the whole consideration time, but over the mean red-noise spectrum of α = 0.72 before approximate Carrington rotation number 1500, and after that the filament activity does not statistiªcally show the period. Wavelet reconstruction indicates that the early data of the filament archive (in and before cycle 16) are more noiseful than the later (in and after cycle 17).

6 illus, 31 ref

017054   Irimia A (Physics and Astronomy Dep, Vanderbilt Univ, Nashville, Tennessee, 37235, USA) : Forbidden transition probabilities of astrophysical interest among low-lying states of V III. J Astrophys Astr 2007, 28(2-3), 157-66.

Electric and magnetic multi pole transitions among lowªlying states of doubly ionized vanadium were computed using the multi-configuration Hartree-Fock (MCHF) method with Breit-Pauli (BP) corrections to a non-relativistic Hamiltonian. Energy levels were deterªmined up to and including 3d² (¹G)4s b ²G_7/2 and computed energies were found to be in good agreement with experiment and other theories. In addition to Einstein A_ki coefficients for some E2 and Ml transiªtions, lifetime data and selected weighted oscillator strengths are also reported.

5 tables, 37 ref

017053   Huang C;Zhao G;Zhang H W;Chen Y Q (Astronomy Dep, Peking Univ, Beijing-100 871, Email: gzhao@bao.ac.cn) : Does Si play a role in the formation of extrasolar planet systems. J Astrophys Astr 2007, 28(2-3), 139-45.

With the high signal-to-noise ratio spectra, author obtained Si abundances of 22 extrasolar planet host stars, and discussed some conªstraints on the planet formation. Using silicon abundance results and other authors' Si abundance studies about planets-harboring stars, author investigated the correlation between the dynamical properties and the silicon abundance. Proposed a hypothesis that higher primordial metallicity in the host stars' birth cloud with higher abundance of Si will make the cloud more sticky to bypass the time scale restriction in planet formation and easier to form the planets.

3 illus, 31 ref

016078   Sharma R;Maharaj S D (NO, , ) : On surface tension for compact stars. J Astrophys Astr 2007, 28(2-3), 133-8.

In an earlier analysis it was demonstrated that genecal relativity give s higher values of surface tension in strange stars with quark matter than neutron stars. Generates the modified Tolman-Oppenheimer-Volk off equation to incorporate anisotropic matter and use this to show that pressure anisotropy provides for a wide range of behaviour in the surface tension than is the case with isotropic pressures. In particular, it is possible that anisotropy drastically decreases the value of the surface tension.

1 illus, 1 table, 30 ref

016077   Rajakumar P;Sanjeevi S;Jayaseelan S; Isakkipandian G;Edwin M;Balaji P;Ehanthalingam G (Geology Dep, Anna Univ, Chennai-600025, Email: prkgtmsa@yahoo.co.in) : Landslide susceptibility mapping in a hilly terrain using remote sensing and GIS. J Indian Soc Remote Sens 2007, 35(1), 31-42.

Remote sensing and Geographic Information System (GIS) are well suited to landslide studies. The aim of this study is to prepare a landslide susceptibility map of a part of Ooty region, Tamil Nadu, India, where landslides are common. The area of the coverage is approximately 10 x14 km in a hilly region where planting tea, vegetables and cash crops are in practice. Hence, deforestation, formation of new settlements and changing land use practices are always in progress. Land use and land cover maps are prepared from Indian Remote Sensing Satellite (IRS 1C - LISS III) imagery. Digital Elevation Model (DEM) was developed using 20 m interval contours, available in the topographic map. Field studies such as local enquiry, land use verification, landslide location identification were carried out. Analysis was carried out with GIS software by assigning rank and weights for each input data. The output shows the possible landslide areas, which are grouped for preparation of landslide susceptibility maps.

13 illus, 8 tables, 14 ref

016076   Prasad J (Harish Chandra Res Inst, , Allahabad-211 019, Email: jayanti@mri.ernet.in) : Effects of the size of cosmological N-body simulations on physical quantities- II: halo formation and destruction rate. J Astrophys Astr 2007, 28(2-3), 117-31.

Shows how errors due to finite box size affect formation and the destruction rate for haloes in cosmological N-body simulations. In an earlier study was analytic prescription of finding the corrections in the mass function given. Following the same approach, in this paper author gave analytical expressions for corrections in the formation rate, destruction rate and the rate of change in comoving number density, and compute their expected values for the power law (n = -2) and LCDM models.

6 illus, 43 ref

016075   Patel N K;Saxena R K;Shiwalkar A (Crop Inventory and Modeling Div, ARG, Resipa Space Application Centre (ISRO), Ahmedabad-380 015) : Study of fractional vegetation cover using high spectral resolution data. J Indian Soc Remote Sens 2007, 35(1), 73-9.

A field experiment was conducted to study the effect of vegetation cover on soil spectra and relationship of spectral indices with vegetation cover. Multi-date spectral measurements were carried out on twelve wheat fields. Five sets of measurements were taken during the growth period of wheat crop. Field reflectance data were collected in the range 350 to 1800 nm using ASD spectroradiometer. Analysis of data was done to select narrow spectral bands for estimation of ground cover. The ratio of reflectance from vegetation covered soil and reflectance from bare soil indicated that spectral reflectance at 670 and 710 nm are the most sensitive bands. Two bands in visible (670 and 560 nm), three bands in near infrared (710, 870 and 1 100 nm) and three bands in middle infrared (1480, 1700 and 1800 nm) were found highly correlated with fractional cover. Vegetation indices developed using narrow band spectral data have been found to be better than those developed using broad- band data for estimation of ground cover.

3 illus, 1 table, 10 ref

016074   Narlikar J V (Inter Univ Centre for Astronomy & Astrophys, , Pune-411 007, Email: jvn@iucaa.ernet.in) : Cosmology and cosmogony in a cyclic universe. J Astrophys Astr 2007, 28(2-3), (NULL).

Discusses the properties of the quasi-steady state cosmological model (QSSC) developed in 1993 in its role as a cyclic model of the universe driven by a negative energy scalar field. We discuss the origin of such a scalar field in the primary creation process first described by F. Hoyle & J. V. Narlikar forty years ago. It is shown that the creation processes which take place in the nuclei of galaxies are closely linked to the high energy and explosive phenomena, which are commonly observed in galaxies at all redshifts. The cyclic nature of the universe provides a natural link between the places of origin of the microwave background radiation (arising in hydroªgen burning in stars), and the origin of the lightest nuclei (H, D, He³ and He⁴). It also allows us to relate the large scale cyclic properties of the uniªverse to events taking place in the nuclei of galaxies. Observational eviªdence shows that ejection of matter and energy from these centers in the form of compact objects, gas and relativistic particles is responsible for the population of quasi-stellar objects (QSOs) and gamma-ray burst sources in the universe. Discusses the major unsolved problems of this integrated cosmological and cosmogonical scheme - the understanding of the origin of the intrinsic redshifts, and the periodicities in the redshift distribution of the QSOs.

1 illus, 80 ref

016073   Martin D;Saha S K (National Bureau of Soil Survey and LandUse Planning, Regfional Center, IARI Campus, New Delhi-110 012, Email: mrteve@rediffmail.com) : Integrated approach of using remote sensing and gis to study watershed prioritization and productivity. J Indian Soc Remote Sens 2007, 35(1), 21-30.

Soil data obtained from soil resource inventory, land and climate were derived from the remote sensing satellite data (Landsat TM, bands 1 to 7) and were integrated in GIS environment to obtain the soil erosion loss using USLE model for the watershed area. The priorities of different sub-watershed areas for soil conservation measures were identified. Land productivity index was also used as a measure for land evaluation. Different soil and land attribute maps were generated in GIS, and R.K,LS,C and P factor maps were derived. By integrating these soil erosion map was generated. The mapping units, found not suitable for agriculture production, were delineated and mapped as non-arable land. The area suitable for agricultural production was carved out for imparting the productivity analysis; the land suitable for raising agricultural crops was delineated into different mapping units as productivity ratings good, fair, moderate and poor. The analysis performed using remote sensing and GIS helped to generate the attribute maps with more accuracy and the ability of integrating these in GIS environment provided the ease to get the required kind of analysis. Conventional methods of land evaluation procedures in terms of either soil erosion or productivity are found not comparable with the out put generated by using remote sensing and GIS as the limitations in generating the attribute maps and their integration. The results obtained in this case study show the use of different kinds of data derived from different sources in land evaluation appraisals.

7 illus, 4 tables, 12 ref

016072   Martin D;Mahapatra S K;Singh S P;Dhankar R P (National Bureau of Soil Survey and Land Use Planning, Regional Centre, IARI Campus, New Delhi-110 012, Email: mrteve@rediffmail.com) : Landfrom analysis of warm humid kumaon himalayas using irs-id data for development of mountainous lands. J Indian Soc Remote Sens 2007, 35(1), 101-6.

2 illus, 20 ref

016071   Mani P;Chakravorty B (Centre for flood Mangement Studies, National Institute of Hydrology, Patna-801 505) : Remote sensing based sedimentation study of maithon reservoir. J Indian Soc Remote Sens 2007, 35(1), 117-20.

2 illus, 1 table, 10 ref

016070   Lopez Corredoira M (Instituto de Astorfisica de Canarias, , C/.Via Lactea, s/n, E-38200 La Laguna (S/C de Tenerife), Spain, Email: martinlc@iac.es) : Some doubts on the validity of the foreground galactic contribution subtraction from microwave anisotropies. J Astrophys Astr 2007, 28(2-3), 101-16.

The Galactic foreground contamination in CMBR anisotropies, especially from the dust component, is not easily separable from the cosªmological or extragalactic component. In this paper, some doubts will be raised concerning the validity of the methods used until now to remove Galactic dust emission and will show that none of them achieves its goal. Reviews the recent bibliography on the topic and discusses critically the metho s of foreground subtraction: the cross-correlation with templates, analysis assuming the spectral shape of the Galactic compoªnents, the "maximum entropy method", "internal linear combination", and "wavelet-based high resolution fitting of internal templates". Second, I analyse the Galactic latitude dependence from WMAP data. The frequency dependence is discussed with data in the available literature. The result is that all methods of subtracting the Galactic contamination are inaccurate. The Galactic latitude dependence analysis or the frequency dependence of the anisotropies in the range 50-250 GHz put a constraint on the maximum Galactic contribution in the power spectrum to be less than ~ 10% (68% L.) for an ~ 1 degree scale, and possibly higher for larger scales. The origin of most of the signals in the CMBR anisotropies is not Galactic. In any case, the subtraction of the galaxy is not accurate enough to allow a "precision Cosmology"; other sources of contamination (extragalactic, solar system) are also present.

1 illus, 85 ref

016069   Li K J;Li Q X;Gao P X;Mu J;Chen H D;Su T W (National Astronomical Observatories/Yunnan Observatory, , CAS, Kunming-650 011, Email: lkj@ynao.ac.cn) : Activity cycle of solar filaments. J Astrophys Astr 2007, 28(2-3), 147-56.

Long-term variation in the distribution of the solar filaments observed at the Observatorie de Paris, Section de Meudon from March 1919 to December 1989 is presented to compare with sunspot cycle and to study the periodicity in the filament activity, namely the periods of the coronal activity with the Morlet wavelet used. It is inferred that the activity cycle of solar filaments should have the same cycle length as sunspot cycle, but the cycle behavior of solar filaments is globally similar in profile with, but different in detail from, that of sunspot cycles. The amplitude of solar magnetic activity should not keep in phase with the complexity of solar magnetic activity. The possible periods in the filament activity are about 10.44 and 19.20 years. The wavelet local power spectrum of the period 10.44 years is statistically significant during the whole consideration time. The wavelet local power spectrum of the period 19.20 years is under the 95% confidence spectrum during the whole consideration time, but over the mean red-noise spectrum of α = 0.72 before approximate Carrington rotation number 1500, and after that the filament activity does not statistiªcally show the period. Wavelet reconstruction indicates that the early data of the filament archive (in and before cycle 16) are more noiseful than the later (in and after cycle 17).

6 illus, 31 ref

016068   Huang C;Zhao G;Zhang H W;Chen Y Q (Astronomy Dep, Peking Univ, Beijing-100 871, Email: gzhao@bao.ac.cn) : Does Si play a role in the formation of extrasolar planet systems. J Astrophys Astr 2007, 28(2-3), 139-45.

With the high signal-to-noise ratio spectra, we obtained Si abundances of 22 extrasolar planet host stars, and discussed some conªstraints on the planet formation. Using our silicon abundance results and other authors' Si abundance studies about planets-harboring stars, author investigated the correlation between the dynamical properties and the silicon abundance. Proposed a hypothesis that higher primordial metallicity in the host stars' birth cloud with higher abundance of Si will make the cloud more sticky to bypass the time scale restriction in planet formation and easier to form the planets.

3 illus, 31 ref

016067   Bhuyan M R;Rajak D R;Oza M (Crop Inventory and Modelling Div, Agricultural Resoures Group-RESIPA Space Applications Center, Ahmedabad-380 015, Email: markand@sac,isro.gov.in) : Quantification of improvements by using awifs over wifs data. J Indian Soc Remote Sens 2007, 35(1), 43-52.

The Advanced WiFS sensor of RESOURCESAT - 1 satellite offers significantly improved specifications compared to the WiFS sensor onboard IRS 1C. P3 and ID satellites. The improvements are in terms of spatial resolution, radiometry (quantisation levels) and number of spectral bands. In the present study, an attempt has been made to quantify the gains due to these enhanced specifications. The study has been carried out in a predominantly agricultural area. For the study reported here, one set of overlapping data acquired on the same day by WiFS and AWiFS sensors has been selected. This eliminates the need of atmospheric correction/ normalization for comparison. The effect of spatial resolution has been studied by applying ISODATA spectral clustering algorithm with number of clusters set at three different levels, viz.. 10. 20 and 30. They are assumed to mimic first, second and third level classification, respectively. Output images were filtered using 3x3 majority filter. Homogeneous polygons having area less than 1/2 and 1 pixel of WiFS were recorded. This indicates the minimum loss by using WiES data. A relative gain of 10 - 15 % is observed due to improvement in spatial resolution. For comparison of radiometry. local variance measure was used. It was observed that local variance is much larger for AWiFS data in comparison with WiFS data. This indicates presence of enhanced local contrast, hence heterogeneity, in AWiFS data over WiFS data. Separability analysis has been carried out to demonstrate improvements due to two additional spectral bands (Green and SWIR).

5 illus, 4 tables, 18 ref

015095   White S M (Astronomy Dep, Maryland Univ, College Park, MD 20742, USA) : Solar radio bursts and space weather. Asian J Phys 2007, 16(2-3), 189-207.

Space Weather is the study of the conditions in the solar wind that can affect life surface of the Earth, particularly the increasingly technologically sophisticated devices that are part of modern life. Solar radio observations are relevant to such phenomena because they generally originate as events in the solar atmosphere, including flares, coronal mass ejections and shocks, that produce electromagnetic and particle radiations that impact the Earth. Low frequency solar radio emission arises in the solar atmosphere at the levels where these events occur: we can use frequency as a direct measure of density, and an indirect measure of height, in the atmosphere. The main radio burst types are described and illustrated using data from Green Bank Solar Radio Burst Spectrometer, and their potential use as diagnostics of Space Weather is discussed.

12 illus, 39 ref

015094   Vats H O (NO, Physical Research Laboratory, Ahmedabad-380 009) : Rotation of the sun and its atmosphere. Asian J Phys 2007, 16(2-3), 291-307.

The rotation of the Sun and its atmosphere is extremely complex. In the recent years a great deal of research work has been carried out on this subject to learn and understand the physics and the consequences of this in the realm of space weather. This article is an attempt to review the important findings and their implications. The main emphasis is on the recent results in this field. The salient rotational features of the solar interior, photosphere, chromosphere and corona will be discussed. These estimates are based on solar observations by satellite and ground based instruments operating at various frequencies in the entire electromagnetic spectrum of the Sun.

11 illus, 53 ref

015093   Subramanian P (NO, Indian Institute of Astrophysics, Koramangala, Bangalore-560 034) : Electron acceleration in solar noise storms. Asian J Phys 2007, 16(2-3), 233-46.

Presents an up-to-date review of the physics of electron acceleration in solar noise storms. Ddescribes the observed characteristics of noise storm emission, emphasizing recent advances in imaging observations. Briefly describes the general methodology of treating particle acceleration problems and apply it to the specific problem of electron acceleration in noise storms. Dwells on the issue of the efficiency of the overall noise storm emission process and outline open problems in this area.

4 illus, 66 ref